Many manufactured products require multiple components to be bonded and welded to a central tube, shaft or hub. In most instances, each component must be bonded to the central component in a separate welding process regardless of the type of welding process used. Consequently, producing such components is difficult, expensive and time consuming. In another example, integrally bladed rotors or “blisks” are critical components in certain aircraft engines. A blisk is a single engine component consisting of a plurality of rotor blades extending radially from a rotor disk or hub. Blisks can be produced using various manufacturing processes, including CNC milling, investment casting, electro-chemical machining, or welding. Heretofore, these conventional manufacturing processes, particularly welding individual rotor blades to the rotor hub have been difficult, expensive and time consuming.
Linear friction welding (LFW) is a process of joining two components which may be made from the same or different materials. The LFW process typically involves pressing the two components together under a large amount of force and rapidly oscillating the components with respect to one another to generate friction at the interface between the two components. The pressure and movement generate sufficient heat to cause the material at the interface to plasticize. Once the material at the interface begins to plasticize, the oscillation is stopped and an increased force is applied. As the plasticized material of both components cools in this static condition, the components are bonded together and a weld is formed. While LFW is suitable in many applications, heretofore, LFW has been limited to bonding only two components together at one time.
The linear friction welding (LFW) apparatus and methods of this invention allows multiple components to be simultaneously bonded to a central shaft, tube or hub using linear friction welding in a single welding process. The LFW apparatus of this invention employs linear friction welding machines, such as the ones available from APCI, Inc. of South Bend, Ind. and disclosed in U.S. Pat. No. 8,070,039 issued on Dec. 6, 2011. The LFW machine generally includes a number of fixtures and press assemblies to hold and press the various work pieces against the central shaft, tube and a vibrating assembly for vibrating the central shaft, tube or hub.
In one embodiment, the LFW apparatus and method of this invention allows multiple work pieces to be bonded to an elongated shaft in a single weld process. The LFW apparatus includes multiple work piece fixtures operatively connected to the press assembly of an LFW machine while the shaft is operatively connected to the vibrating assembly of the LFW machine. In another embodiment, LFW apparatus and method of this invention allows multiple rotor blades to be bonded radially around a central rotor hub in a single weld process to create a blisk. In this embodiment, a collet assembly holds and presses the blades against the rotor hub, which is shiftably disposed within the collet assembly and supported by a mounting fixture. The collet assembly is operatively connected to the press assembly of the LFW machine, which uniformly presses the blades inward radially against the rotor hub of the blisk. The rotor hub is supported by a fixture operatively connected to the vibrating assembly of the LFW machine, which vibrates the hub axially within the collet assembly.
In each embodiment, the weld is formed by the LFW machine vibrating the central work piece axially while the other work pieces are pressed against the central piece under an initial load or “weld pressure.” Friction between the work pieces causes the material at the weld surfaces to plasticize. When the vibration is stopped, the work pieces are pressed together under a final load or forging pressure, which forms the weld interface bonding the pieces together.
The apparatus and method of the present invention may take form in various systems and components, as well as the arrangement of those systems and components. The above described features and advantages, as well as others, will become more readily apparent to those of ordinary skill in the art by reference to the following detailed description and accompanying drawings. The drawings are only for purposes of illustrating exemplary embodiments and are not to be construed as limiting the invention.